swift2からswift4へのコンバートエラーについて dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), { let icloudURL = self.makeICloudURL("test.txt") dispatch_async(dispatch_get_main_queue(), { if icloudURL != nil { self.writeICloud1(icloudURL!) } else { self.showAlert("", text: "iCloudURL") } }) }) DispatchQueue.global(qos: .default).async { let icloudURL = self.makeICloudURL(fileName: "test.txt") dispatch_async(dispatch_get_main_queue(), { if icloudURL != nil { self.writeICloud1(icloudURL!) } else { self.showAlert("", text: "iCloudURL") } }) }

Xcode 9migratorSwift 2?

* Xcode 8migratorSwift 2Swift 3
* Xcode 9migratorSwift 3Swift 4







* * *



`dispatch_async(` __`, {` __`})`
↓
__`.async {` __`}`

`dispatch_get_global_queue(...)`
↓
`DispatchQueue.global(...)`



`dispatch_async`, `dispatch_get_global_queue``dispatch_get_main_queue`CGCDSwift3Swift2→4

* * *

`dispatch_async``dispatch_get_main_queue()``DispatchQueue.main`




DispatchQueue.global(qos: .default).async {
let icloudURL = self.makeICloudURL(fileName: "test.txt")
DispatchQueue.main.async {
if icloudURL != nil {
self.writeICloud1(icloudURL!)
} else {
self.showAlert("", text: "iCloudURL")
}
}
}


38:


dispatch_async(dispatch_get_main_queue(), {

})





DispatchQueue.main.async {

}




* * *